The present invention relates generally to a synchronous control system of rotary presses, and more particularly to a synchronous control system of rotary presses comprising a plurality of printing mechanisms driven individually by separate driving means that rotate N turns (N is a natural number) as a plate cylinder rotates one turn, a control section for controlling each driving means, so that printing images are matched with each other and printed on a paper web sequentially passing through each printing mechanism.
Synchronous control systems for rotary presses of a type comprising a plurality of printing mechanisms driven individually by separate driving means, a control section for controlling each driving means, so that printing images are matched with each other and printed on a paper web sequentially passing through the printing mechanisms are disclosed in Japanese Published Unexamined Patent Application No. Hei-10(1998)-32992 and Japanese Patent Publication No. 2964238, for example.
The synchronous control system for rotary presses disclosed in Japanese Published Unexamined Patent Application No. Hei-10(1998)-32992 accomplishes synchronous control of rotary presses by monitoring changes in the phase difference between the master shaft mechanical movement and the slave shaft mechanical movement, that is, changes in the distance (phase difference) between the Z-phase signal of a master-side rotary encoder with Z phase connected to a master-shaft driving motor for driving a master-shaft mechanical movement and the Z-phase signal of a slave-side rotary encoder with Z phase connected to a slave-shaft motor for driving a slave-shaft mechanical movement, so that when the phase difference is changed, the slave-shaft driving motors are controlled to correct the change in the phase difference.
The synchronous control system for rotary presses disclosed in Japanese Patent Publication No. 2964238 controls motors for driving driven cylinders by providing phase signal output means to a reference cylinder, and driven cylinders, such as a plate cylinder and a blanket cylinder, each driven by different motors, causing the driving motors for the reference and driven cylinders to operate based on a speed instruction output by a speed command center, outputting a phase-difference signal by processing a signal from the phase signal output means for the reference cylinder and a signal from the phase signal output means for the driven cylinders, both being outputs as the result of the operation of the driving motors, and correcting the speed instruction to the driving motors for the driven cylinders based on the phase-difference signal.
The aforementioned prior-art synchronous control systems have the following problems.
That disclosed in Japanese Published Unexamined Patent Application No. Hei-10(1998)-32992 monitors the phase difference between the driving motors, and corrects the phase difference between the driving motors by regarding the change in the phase difference as the change in the phase difference between the mechanical movements driven by the driving motors. Consequently, it is effective so long as the rotation of driving motors agrees with the rotation of the mechanical movements, that is, the mechanical movements rotate one turn as the driving motors rotate one turn. However, when the rotations of the driving motors and the mechanical movements do not agree with each other, that is, when the mechanical movements rotate only xc2xd turns or ⅓ turns as the driving motors rotate one turn, the rotational phase of the mechanical movements would remain shifted by xc2xd or ⅓ turns, the phase shift could not be eliminated unless the entire system is started after the rotational phase of the mechanical movements is corrected to an almost proper phase. For this reason, this synchronous control system has not been put into practical use for rotary presses where the rotation of the mechanical movements is not in a one-for-one relation with that of the driving motors (driving means).
That disclosed in Japanese Patent Publication No. 2964238, on the other hand, obtains a phase difference between both cylinders by processing the phase signal of a reference cylinder and the phase signals of other driven cylinders, and corrects the phase difference by changing the rotational phase of motors for driving the other driven cylinders on the basis of the phase difference. Consequently, the synchronous control system disclosed in Japanese Patent Publication No. 2964238 has no such problems as experienced in that disclosed in Japanese Published Unexamined Patent Application No. Hei-10(1998)-32992. The synchronous control system disclosed in Japanese Patent Publication No. Hei-10(1998)-32992, however, uses transmission mechanisms not only between the reference cylinder and the motor for driving it, but also between the other driven cylinders and the motors for driving them. The xe2x80x9cplay,xe2x80x9d such as backlash, inherent in these transmission mechanisms tends to allow errors to creep into any of the phase signals of the reference cylinder and the other driven cylinders, making the signals unstable and inaccurate. Generating control signals for the driving motors by processing such phase signals may result in unstable control signals, making the control of the driving motors unstable and inaccurate. Thus, it has taken long time before the phase becomes stable at proper levels. For this reason, the conventional controlling method of plate cylinder rotation in rotary presses has often caused defective printing (spoilage) due to phase shifts before the phase becomes stable. From the foregoing, it may be appreciated that a need has arisen for countermeasures to cope with these problems.
The present invention has been conceived in view of the aforementioned problems. It is an object of the present invention to provide a synchronous control of rotary presses that can be applied to printing mechanisms having plate cylinders rotating 1/N (N being a natural number) turns for one turn of driving means, can control the driving means quite accurately, and can stabilize rotation quickly, accordingly stabilizing the rotation of the plate cylinders and reducing spoilage due to phase shifts.
It is a more specific object of the present invention to provide a synchronous control system for rotary presses where the rotation of plate cylinders is synchronized by using a plate cylinder signal generated for one turn of the plate cylinders, a first pulse signal output in proportion to the amount of angular displacement along with the rotation of the driving means, and a second pulse signal output for one turn of the driving means, setting in advance a driving reference comprising a reference speed and a reference phase, replacing the rotational phase of the plate cylinders for matching printing images with a predetermined reference with a rotational phase of the driving means corresponding to the aforementioned rotational phase, converting a shift between the driving means rotational phase for matching printing images with a predetermined reference and the driving means rotational phase in the normal state into the number of outputs of the first pulse signals, which is set as a correction value, producing a virtual feedback phase by shifting the driving means rotational phase by the amount of the correction value, and controlling so as to synchronize the driving reference phase with the virtual feedback phase of each driving means.
It is another object of the present invention to provide a synchronous control system for rotary presses where a plate cylinder signal output for one turn of the plate cylinders, a first pulse signal generated in proportion to the amount of angular displacement in accordance with the rotation of the driving means, a second pulse signal output for one turn of the driving means, and a driving reference comprising a driving reference speed and a driving reference phase based on a third pulse signal and a fourth pulse signal are set, the output timing of the fourth pulse signal with respect to the third pulse signal is set equal to the output timing of the second pulse signal with respect to the first pulse signal; a phase correction value for correcting a feedback phase, a driving reference speed signal and a driving reference phase signal based on the aforementioned driving reference, a feedback speed signal of the driving means based on the first pulse signal, and a virtual feedback rotational phase signal obtained by correcting by the amount of the aforementioned phase correction value the driving means feedback phase based on the first pulse signal, the second pulse signal and the plate cylinder signal are provided; and a control signal is output by correcting the drive reference speed signal with a signal relating to the difference between the drive reference phase and the virtual feedback rotational phase and the feedback speed signal, so that the operation of printing mechanisms can be controlled with the control signal.
It is still another object of the present invention to provide a synchronous control system for rotary presses where the synchronous control of a rotary press is accomplished by setting a plate cylinder signal output for one turn of the plate cylinders, a first pulse signal generated in proportion to the amount of angular displacement in accordance with the rotation of the driving means, and a second pulse signal generated for one turn of the driving means, and a driving reference comprising a driving reference speed and a driving reference phase, setting the output timing of the fourth pulse signal with respect to the third pulse signal equal to the output timing of the second pulse signal with respect to the first pulse signal, generating a drive reference speed signal based on the driving reference, a driving reference phase signal based on the driving reference, a feedback speed signal of the driving means based on the first pulse signal, a phase correction signal for correcting the driving means feedback phase of the driving means based on the first pulse signal, the second pulse signal and the plate cylinder signal, a virtual feedback phase signal obtained by correcting the feedback phase with the phase correction signal, a phase difference between the driving reference phase signal and the virtual feedback phase signal, a corrected control signal obtained by correcting the driving reference speed signal based on the outputs of the phase difference signal and the feedback speed signal, and controlling the driving means of the printing mechanisms using the corrected control signal via a motor driver.
The operation of the present invention is such that the rotational phase of plate cylinders for matching printing images with a predetermined reference is replaced with the driving means rotational phase corresponding to the rotational phase, and a difference between the driving means rotational phase for matching printing images with a predetermined reference and the driving means rotational phase in the normal state, that is, a difference in the amount of rotation of driving means is converted into the number of outputs of the first pulse signals that is set as a correction value.
In this state, a driving reference setting section is operated to output a driving reference comprising a driving reference speed and a driving reference phase. With this, each driving means begins rotation at the reference speed.
As each driving means rotates, a feedback signal output section generates a first pulse signal proportional to the amount of angular displacement of the driving means and a second pulse signal for one turn of the driving means, the plate cylinders are caused to rotate by the driving means, and a plate cylinder signal output section generates a plate cylinder signal for one turn of the plate cylinders.
In a control section, a virtual feedback phase is produced by shifting the rotational phase of each driving means by the amount of the correction value based on the first pulse signal, the second pulse signal and the plate cylinder signal, and control is accomplished so as to synchronize the driving reference phase and the virtual feedback phase of each driving means to synchronize the rotation of each plate cylinder.
This arrangement can prevent the phase from shifting at the start of control of plate cylinders based on the difference caused by the rotation by N turns of the driving means for one turn of the plate cylinders, making it possible to achieve synchronous control of the driving means with high accuracy. This arrangement also enables to quickly stabilize the rotation of the driving means. Furthermore, all these effects work synergistically in stabilizing the rotation of the plate cylinders and reducing spoilage, such as defective printing, due to shifts in the rotational phase of the plate cylinders.